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Q. Frequency-controlled induction-motor drives ?
The converters employed for variable-frequency drives can be classified as:
• Voltage-source inverter (which is the only one considered here)
• Current-source inverters
• Cycloconverters, which allow a variable-frequency ac supply with voltage-source or current-source characteristics obtained from a fixed-frequency voltage source.
Acommon symbol for the self-commutated semiconductor switch is shown in Figure. The control signal (either voltage or current) is denoted by CS, and the diode gives the direction in which the switch can conduct current. GTOs, power transistors, and MOSFETs are classified as self-commutated semiconductor devices because they can be turned off by their respective control signals: GTOs by a gate pulse, a power transistor by a base drive, and a MOSFET by a gate-to-source voltage. A thyristor, on the other hand, is a naturally commutated device that cannot be turned off by its gate signal. A thyristor combined with a forced commutation circuit behaves like a self-commutated semiconductor device, however. The self-commutation capability makes its turnoff independent of the polarity of the source voltage, the load voltage, or the nature of load. Self-commutated semiconductor switches are suitable for applications for converters fed from a dc source, such as inverters and choppers.
Q. The flux-density distribution in the air gap of a 60-Hz, two-pole, salient-pole machine is sinusoidal, having an amplitude of 0.6 T. Calculate the instantaneous and rms value
Capacitor-input filter: The capacitor-input filter, as well called pi filter because of its shape which looks like the Greek letter pi, is a sort of electronic filter. Filter
One circuit has resistor 40? connected in series with inductor 15H and dc voltage 220V. Calculate: i) Time constant ii) Current at time (i) iii) Current at time 0.0
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Flag Registers Flag register is also an 8 bit register. Out of 8 bit five are defined as flags to indicate status of the accumulator hence it is also called status reg
Norton's theorem procedure: 1. Remove R L from the circuit. Search I N by shorting links output terminal. 2. Search R N by short-circuit voltage source or open-circuit
Explain Loads - Generation and Absorption of Reactive Power A load at 0.95 power factor implies a reactive power demand of 0.33 kVAr per kW of power. When planning a network, i
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